The present invention generally relates to a system that manages the retard limit in internal combustion engines.
Internal combustion engines are designed to maximize power while meeting exhaust emission requirements and minimizing fuel consumption. In a conventional spark-ignition (“SI”) engine, combustion is initiated at the spark plug by an electrical discharge. Recent advances in the powertrain electronic controls (“PCM”) make it possible to employ online spark adjustment to optimize the engine operation in terms of power, fuel economy, and emissions. However, the range of ignition timing is often limited by knock in the advance direction and by combustion instability (i.e., partial burn and misfire) in the retard direction. Since the feasible ignition timing range depends on the engine operating conditions, it is desirable to extract online in-cylinder combustion information to optimally adjust the operational boundaries of the engine.